Add mode tests

Author: BCSharp

tests/IronPython.Tests/Cases/CPythonCasesManifest.ini

@@ -7,9 +7,6 @@ Timeout=120000 # 2 minute timeout
 [CPython.ctypes.test_as_parameter]
 Ignore=true
 
-[CPython.ctypes.test_bitfields] # IronPython.modules.type_related.test_bitfields_ctypes_stdlib
-Ignore=true
-
 [CPython.ctypes.test_errno]
 Ignore=true
 Reason=Current implementation of get_last_error needs to be debugged